Dock seals form a weather seal between a trailer and a loading bay. Various types of dock seals have been developed and are know in the industry. Compressible seals that engage the sides and roof of the trailer are disclosed in U.S. Pat. Nos. 3,230,675; 4,213,279; 4,679,364 and 6,170,205. Inflatable or expanding seals that engage the sides and top of a trailer are described in U.S. Pat. Nos. 3,714,745; 3,939,614; 4,020,607 and 5,109,639. A loading dock shelter with side curtains mounted to side frames and a head curtain mounted to a top wall is disclosed in U.S. Pat. No. 3,403,489. A loading dock shelter with side and head curtains and compressible springs is disclosed in U.S. Pat. No. 3,826,049. A canopy with vertical side members and compressible springs and a horizontal member is disclosed in U.S. Pat. No. 4,365,452. A multi-seal dock-seal with a top seal and vertical side seals equipped with both wipe seals and compression seals is disclosed in U.S. patent application Ser. No. 15/079,021.
There are also a wide variety of pit seals. Some pit seals are located along the sides of the leveler as in U.S. Pat. Nos. 4,557,008 and 5,442,825. Pit seals help prevent weather, debris, insects and birds from entering the loading bay when the leveler is lowered to engage a trailer parked in the loading bay. When the leveler is raised, anything in the pit can be blown or otherwise make its way into the loading bay. Other pit seals are located under the leveler toward the front of the pit to prevent weather, debris, insects and birds from entering the pit. Examples of these pit seals are shown in U.S. Pat. Nos. 4,293,969; 4,422,199; 4,682,382; 6,502,268; 7,146,673; 7,594,290 and 8,006,338. They include inflatable seals, collapsing sheet seals, repositionable panel seals, hanging seals or a combination of the same.
Various problems exist with conventional loading dock pit seals. Pit seals located along the sides of the leveler have several problems. When the seals are formed by sheets of material secured to the sides of the leveler and pit wall as in U.S. Pat. No. 4,557,008, the sheets are easily pinched and sheared between the leveler and the side edges of the pit. These sheet seals are also highly impractical for vertically stored levelers. When the seals are formed by a resilient, compressible material secured along the sides of the leveler as in U.S. Pat. No. 5,442,825, the seals are pushed into and pulled out of compressed engagement with the pit edges and walls each time the leveler is raised and lowered. This forced engagement wears on and damages the seals. The greater the compressed sealing force between the seal and the pit walls the greater the wear and tear of the seal. Leveler misalignment relative to the pit walls creates an additional problem. When one side of the leveler is closer to one pit wall and the other side of the leveler is farther away from the pit wall, the result is excessive wear on one seal and an inadequate seal or gap in the seal for the other side.
Pit seals with multiple moving and fixed parts are inherently problematic. An example of such a device is shown in U.S. Pat. No. 8,006,338. This device includes rigid panels, dowels, pins, brackets, leavers, springs, extensions, rollers, mating concave and convex surfaces and weather-stripping. Binding, jamming, loosening, misalignment or breakage of any number of these components can result in an inadequate seal or complete failure of the device. An inflatable pit seal is shown in U.S. Pat. No. 4,293,969. This pit seal includes a blower motor and inflatable air bag mounted on beams extending up from the pit floor, along with straps and flaps to guide the expansion and contraction of the air bag. These seals require additional electrical wiring and are inoperable during a power outage. Many of the components forming these seals are located inside the pit, and inhibit the necessary periodic cleaning of the pit. The manufacturing, installation and maintenance costs associated with these types of pit seals renders them expensive and impractical for many loading bay installations.
Curtain seals that attach to and hang from the leveler and seal against the pit floor have additional problems. Examples of such seals are in U.S. Pat. Nos. 4,422,199 and 7,594,290. The constantly accumulating dirt and debris on the pit floor results in inadequate sealing. Adhesive or Velcro strips that secure the curtain to the floor lose their holding strength and become ineffective. When the leveler is lowered and the curtain folds or collapses, it can extend forward and be pinched and damaged between the front of the leveler and the pit floor. Structures to ensure the curtain folds rearwardly are awkward to install and negotiate when cleaning the pit. Rigid hanging structures pose injury risks to the persons cleaning the pit or servicing the leveler.
The present invention is intended to solve these and other problems.